Exemplary embodiments of the present invention relate to a direct-fired supercritical CO2 power generation system, and more particularly, to a direct-fired supercritical CO2 power generation system capable of preheating combustion air and recovering heat from exhaust gas by itself using supercritical CO2, in which no phase change occurs, as a working fluid.
Thermal power generation is generally classified into steam power generation, internal combustion power generation, and special thermal power generation according to heat sources and motors.
Steam power generation is a method of obtaining mechanical energy by generating steam using thermal energy generated when burning fossil fuel such as coal or oil and by supplying the steam to a heat engine, and of obtaining electrical energy by rotating a rotary machine using the mechanical energy. Nuclear power generation is performed in the same manner as using coal or heavy oil except that nuclear power is used as heat generated when burning fuel, and is included in steam power generation. Internal combustion power generation is a method of obtaining mechanical energy by directly using high-pressure gas generated when gas or liquid fuel is evaporated and then ignited/exploded, and of obtaining electrical energy by rotating a rotary machine using the mechanical energy. This internal combustion power generation is preliminary power generation that uses a diesel engine as a motor, and has been used for a long time. Special thermal power generation includes heat-supply power generation, waste heat power generation, two-flow type power generation, geothermal power generation, gas turbine power generation, etc. The gas turbine power generation has been used for independent power generation, together with the internal combustion power generation.
However, the conventional thermal power generation has a problem in that the loss of a turbine occurs due to moisture since a two-phase fluid is present at the outlet of the turbine, whereby the turbine has a limited efficiency. In this regard, since energy, which is required to change the phase of water as a working fluid, must be supplied during the thermal power generation, the heat exchange between a heat source and a working fluid and between a cooling source and a working fluid may be inefficient. In addition, gas-water separation may occur since a drum is installed in a direct-fired heater, and a system and the constituent devices thereof may be complicated in design since steam must be extracted from the turbine to increase the temperature of water supplied thereto in order to enhance the overall efficiency of the system.